The present invention relates to an elastic boot of the type intended to be connected by a front end region to a first rotary member and by a rear end region to a second rotary member, the rear end region of the boot being equipped, on the one hand, around at least part of its periphery, the directrix curve of which has a transverse outline exhibiting points of inflection, with a radially projecting enlargement intended to be housed in a groove of the second rotary member so as to hold the rear end region of the boot axially in place with respect to the second rotary member and, on the other hand, with sealing means intended to bear on the second rotary member.
The invention applies in particular to constant-velocity tripot transmission joints.
Such joints allow rotary movement to be transmitted between a first shaft bearing a male element or tripod and a female element or bell housing which rotates as one with, for example, the output side gear of a differential.
The tripod has three arms each bearing a rolling assembly. Each rolling assembly is intended to roll along a pair of tracks formed in the bell housing. The tripod and the tulip have ternary symmetry.
A boot as defined above is therefore connected by its front end region to a first shaft and its rear end region is slipped onto a front end region of the bell housing so as to protect the joint against external agents and hold a lubricant therein.
In general, the bell housing is made partly by forging and in cross section has three lobes which are convex and farther from the longitudinal axis of the bell housing, and three concave parts closer to its longitudinal axis. The terms xe2x80x9cconcavexe2x80x9d and xe2x80x9cconvexxe2x80x9d are to be understood as meaning with respect to the outside of the bell housing. Each convex lobe internally defines a pair of tracks for a rolling assembly. The concave parts each connect two convex lobes.
The groove that houses the retaining enlargement runs discontinuously around the radially outer surface of the bell housing. This groove is machined in each of the convex lobes by turning.
The rear end region of the boot has an internal cross section of an overall shape that complements that of the cross section of the radially outer surface of the bell housing. The retaining enlargement, which extends radially into the boot, has a peripheral extent that corresponds to that of the retaining groove in the bell housing.
The sealing means generally comprise at least two continuous peripheral lips which extend radially toward the inside of the boot, and one of which is located axially forward of the enlargement and the other of which is located to the rear of the enlargement.
If the accommodating groove in the bell housing is machined by copy turning, that is to say with the cutting tool moved, and therefore material removed, both axially and radially, one flank, generally the rear flank, of the housing groove will be relatively steeply inclined with respect to the radial direction. The corresponding sealing lip, generally the rear lip, will therefore have to be spaced axially a relatively long distance away from the enlargement so that it does not bear on a discontinuous surface and is thus able to fulfil its sealing function.
This constraint therefore entails a relative large axial extent of the rear end region of the boot slipped onto the front end region of the bell housing.
If the housing groove in the bell housing is produced by plunge turning, that is to say with radial cutting tool movement and radial removal of material, the inclination of the flanks of the groove with respect to the radial direction is more limited and the axial extent of the rear region of the boot slipped onto the bell housing can therefore be shorter.
The object of the invention is to provide a boot of the aforementioned type which can be used in transmission joints in which the housing groove in the bell housing is made at low cost by copy turning or plunge turning while at the same time ensuring a good seal, and in which the rear end region that collaborates with the bell housing of the joint has a limited axial extent.
To this end, the subject of the invention is an elastic boot of the aforementioned type, characterized in that the sealing means are located axially on one and the same side with respect to at least part of the enlargement that retains the rear end region of the boot.
According to some particular embodiments, the boot may include one or more of the following features taken in isolation or in any technical feasible combination:
the sealing means are located axially on the same side of the entirety of the enlargement that retains the rear end region of the boot,
the sealing means are located forward of said part of or of the entirety of the enlargement that retains the rear end region of the boot,
the sealing means comprise at least one lip which extends from said rear end region of the boot radially in the same direction as the retaining enlargement,
said or each sealing lip extends approximately around the entire periphery of the rear end region of the boot,
said or each sealing lip extends roughly continuously around the entire periphery of the rear end region of the boot,
the retaining enlargement extends discontinuously around the periphery of the rear end region of the boot,
the rear end region of the boot has a groove for housing a member for clamping the rear end region of the boot onto the second rotary member,
the groove that houses the clamping member is located axially, with respect to at least part of the enlargement that retains the rear end region of the boot, on the same side as the sealing means,
the retaining enlargement extends radially inward from the rear end region of the boot.
A further subject of the invention is a transmission joint comprising a first and a second rotary member and a boot connected by a front end region to the first rotary member and by a rear end region to the second rotary member, characterized in that the boot is a boot as defined hereinabove, in that the second rotary member has, around at least part of its periphery, a groove in which the enlargement that retains the rear end region of the boot is housed, and in that the boot sealing means bear on the second rotary member axially on the same side with respect to at least part of the groove that houses the retaining enlargement.
According to particular embodiments, the transmission joint may include one or more of the following features taken in isolation or in any technically feasible combination:
the boot sealing means bear on the second rotary member axially on the same side with respect to the entirety of the groove that houses the retaining enlargement,
the boot sealing means bear on the second rotary member forward of said part of or of the entirety of the groove that houses the retaining enlargement,
it comprises a member for clamping the rear end region of the boot onto the second rotary member, and the clamping member is arranged axially, with respect to at least part of the enlargement that retains the rear end region of the boot, on the same side as the sealing means,
the groove that houses the retaining enlargement is formed in a radially outer surface of the second rotary member, and the retaining enlargement extends radially inward from the rear end region of the boot.